Field of Invention
The present invention relates to an image sensor circuit with a power noise filtering function, and a control method thereof; particularly, it relates to such an image sensor circuit which filters a power noise by way of differential amplification, and a control method thereof.
Description of Related Art
FIG. 1 shows a schematic diagram of a typical complementary metal-oxide-semiconductor (CMOS) image sensor array circuit 1. As shown in FIG. 1, the CMOS image sensor array circuit 1 includes: an image sensor array 2, a row circuit 3, and a column circuit 4, wherein the image sensor array 2 includes plural image sensing units 10. As shown in the figure, the plural image sensing units 10 are arranged in rows and columns, and operate similarly to a digital memory circuit. The row circuit 3 decodes a row position and the column circuit 4 decodes a column position, and the content in the addressed image sensing unit 10 is picked up to generate an analog image signal. An analog-to-digital converter (ADC) circuit (not shown) converts the analog image signal to a digital image signal DIS1. In the column circuit 4, each column includes one ADC circuit to convert the analog image signal to the digital image signal DIS1.
In the prior art, the column circuit 4 first converts the analog image signal to the digital image signal DIS1 by the ADC circuit, and amplifies the digital image signal DIS1 afterward. The aforementioned operation sequence limits the resolution. Besides, the power noise and dark current cancellation are also performed on the digital image signal DIS1. This also degrades the quality of displayed image according to the digital image signal DIS1.
In view of the above, to overcome the drawbacks in the prior art, the present invention proposes an image sensor circuit with power noise filtering function and a control method thereof, which filter the power noise of the analog image signal by a differential amplification operation between the image sensed signal and the power noise signal, before the digital image signal DIS1 is generated.